Transducer mechanism



'Dec. 6, 1949 G. c. NEWTON, JR

TRANSDUCER MECHANISM 2 Sheets-Sheet 1 Filed Jan. 10, 1944 IN VEN TOR.

m W C II EM 6 kw a ATTORNEYS 1949 s. c. NEWTON, JR 2,490,150

7 TRANSDUCER MECHANISM Filed Jan. 10, 1944 2 Sheets-Sheet 2 ITI INVEN TOR. 650/?65 c. A/W7'0/V,Jr.

A 7 TOR .\'E Y5 Pea-ma 1)....6, 1949 UNITED STATES PATENT OFFICE TRANSDUCER MECHANISM George C. Newton, Jr., Hempstead, N. Y. Application January 10, 1944, Serial No. 517,761

20 Claims.

My invention relates to improvements in transducers of the type that combine a power amplifier and a characteristic transformertherefor. By power amplifier is meant any device which may be used to increase the power, displacement or force level of an input rotation or translation. A hydraulic ram controlled by a slide valve supplied with oil from a pump, and a double disk friction type clutch with output member damped, are typical examples. The inherent characteristic" of such devices is the relationship existing between the input and output when no mechanism for modification or transformation is imposed. This characteristc may be described in terms of differential equations, steady-state frequency response to simple harmonic input, or, qualitatively in words. A mechanism used to transform the inherent characteristic of a power amplifier is here defined as a characteristic transformer. The resulting characteristic of the combination of a power amplifier and a characteristic transformer is here defined as the "derived characteristic. The derived character- I istic may, like the inherent characteristic, be described in terms of differential equations, steady-state frequency response, or qualitatively in words. 7 i

A power amplifier by itself is a transducer; a characteristic transformer, and a combination of a power amplifier and a characteristic transformer are also transducers. Generally, however, the word transducer will be reserved for the overall combination of power amplifier and characteristic transformer.

If a simple power amplifier were used as a transducer withno characteristic transformer, the transducer characteristic resulting would simply be the inherent characteristic of the power amplifier. For some applications this might be entirely satisfactory but frequently, especially in applications involving automatic control systems, the inherent characteristic is not as suitable as some other characteristic. As an example, take a simple slidevalve-controlled hydraulic ram. This type of power amplifier has an inherent characteristic which tends under some conditions to be an output (ram) velocity be proportional to the output displacement of the power amplifier, and if simple proportional to error type of automatic control-is created by suitable coupling of the power ram or motor displacement to the input valve of the amplifier, an unstable system will result. A characteristic transformer could be designed so that its in- 5 corporation in the transducer containing the power amplifier would result in a stable system.

One object of my invention is to make possible the use of power amplifiers, which may have limited or unsuitable inherent characteristics, in automatic control systems by means of characteristic transformers designed to give the resulting transducers less limited or more suitable characteristics. To continue with the example of the preceding paragraph, one method of circumventing the difliculty described is to alter the inherent characteristic of the power amplifier by combining it with a characteristic transformer so that the combination is a transducer which has a derived characteristic of output position approximately proportional to input displacement.

It is sometimes desirable in a single automatic control system to use a transducer of one characteristic under one condition and of another characteristic under another condition, the same I transducer serving to provide both characteristics. The inputs to the transducer may be alike in form or different in form under these two conditions and the transition from the one condition of operation to the other may be automatic or otherwise. A transducer capable of more than one characteristic is frequently needed when some quantity in the automatic control system must be limited or bounded.

A further object of my invention is to provide a transducer which is capable of automatically changing its characteristic when an input ele- 'ment operated by a limit mechanism or other mechanism is actuated.

An embodiment of my invention is shown in the accompanying drawing, in which:

Figure 1 is a perspective view, partly in section, of a transducer incorporating the invention;

Figure 2 is a schematic diagram of an automatic control system in which the transducer of Figure 1 may be used; and

Figure 3 is an elevation of a vibrator used for introducing dither.

For purposes of illustrating my invention, a hydraulic power amplifier of'the slide-valve-controlled, piston type is used in order to give a. concrete example, although there are other power amplifiers that will work as well. The hydraulic power amplifier illustrated in Figure 1 comprises 55 a sleeve valve I having a sleeve 2 and a pilot 8 provided with a stem 4, and a cylinder having a piston 6 provided with a piston rod I, all mounted within a housing 8, although the valve may be in a housing separate from the cylinder and piston. Oil under pressure is fed to the sleeve 2 through a pipe 9, passing thence to the cylinder 5 through passages ill or II depending upon the setting of the sleeve valve I as effected by pilot stem 4. The input element of this power amplifier is the stem 4 and the output element is the piston rod I.

The inherent characteristic of the hydraulic power amplifier is, to a simple approximation,

- that displacement of the input yields a velocity of the output, the latter proportional to the former. In Figure 1 this means that displacement of the pilot 3 with respect to the sleeve 2 produces a velocity of piston 6. This is accomplished by valving oil through the sleeve from oil passage 9, to oil passage in, or I I, depending upon the directiOn of the relative displacement of the pilot 3 and sleeve 2. Piston 6 is forced to move to accommodate the oil flowing into'its cylinder 5 from passage III, or H, and the oil displaced on the opposite side is discharged through passage I, or II), respectively, whence the oil discharges through the sleeve 2 and out the open ends. The position of the sleeve 2 with respect to the housing 8 is controlled by a sleeve stem I2. Generally, the sleeve 2 is kept stationary except for adjustments or for a small amplitude vibration, sometimes referred to as dither," which is used to reduce the effects of friction and backlash within or without the transducer. Friction may sometimes be reduced by rotating the sleeve instead of dithering it. Any dither used is neglected from here on as it may be considered simply as a small periodic motion superimposed upon the motions to be described. The oil available at oil passage 9 comes from a source not shown in Figure 1. Motion is communicated to the pilot 3 by the pilot stem 4. For purposes of simplifying the discussion, the hydraulic forces and coulomb friction on the pilot will be neglected; these are able to be rendered small by proper design and the use of the hydraulically balanced pilot illustrated. Effects of load forces on the piston 6 are to cause departure from the characteristic attributed above but, if available hydraulic forces are large relative to the load forces, it is justifiable in the name of simplicity to omit consideration of the latter.

' As stated above, the inherent characteristic of the hydraulic power amplifier to a first approximation is that displacement of the input yields a velocity of the output. Suppose now that it is desired to have a different characteristic of the transducer as a whole. Suppose further that it is desired that the derived characteristic approximately be: for transient disturbances or for short time considerations, a position of the output element proportional to the force applied on the input element; and, for steady-state operation or for long time considerations, a position of the output element dependent upon the force impulse, that is the area under the force-time curve of the force applied to the input element. This is accomplished by the characteristic transformer of my invention as shown in Figure 1 and the man ner of effecting these ends is described in the following paragraphs. All parts within the housing 8 constitute the power amplifier of this transducer; the rest of the mechanism of Figure 1 constitutes the characteristic transformer.

The control shaft l3, the primary input element of the transducer, is connected by a crank M to the pilot stem 4, the input element of the power amplifier. Let an external agency (not shown) apply a torque to the control shaft. This causes the shaft to turn in the direction of the applied torque; the turning is limited by the restraint of springs l5, l6 and II. (In transient or short time considerations the expander shaft IB-to be described prese'ntlymay be considered substantially stationary on account of the damper attached thereto and therefore spring ll acts as a simple restraint.) The turning of the control shaft 13 causes pilot stem 4 to move. As a consequence, piston 6 takes on a velocity and moves clasp head [9 mounted on one end of it in such a direction as to increase the restraining torque on the control shaft I3 through the agency of spring IS. The pilot stem 4 is thus moved toward its original position which it reaches when clasp head I9 is displaced sufficiently so that a torque balance exists between the torque applied to the control shaft and the restraints imposed by the springs. At this point action ceases (except for expander action to be later described) In order that stability be assured it is sometimes necessary that damping be incorporated in the agency which applies torque to the control shaft or in the input element of the power amplifier (there is some damping inherent in a hydraulic power amplifier input). Adjustment of the neutral position of the parts is obtained by means of the zero adjust nut 20 which may be moved by zero set screw 2| which is carried in journals (not shown) that are fixed with respect to the apparatus as a whole. (When dither is introduced by means of axial vibration of zero set screw 2|, the journals are not fixed, but are vibrated with respect to the apparatus as a whole; this modification is discussed below. From the foregoing it can be seen that spring coupling between the primary input element of this transducer, control shaft l3, and the output element, piston rod 'L makes possible a derived characteristic which for transient or short time considerations is an output displacement proportional to input torque.

Turning our attention now to the long time or steady-state effects: whenever clasp head 19 is displaced, a torque is applied to expander shaft I8 through a spring 22 and a velocity is imparted thereto which is determined by the damper.

torques and spring torques. A damper 23 is shown comprising a damper disk and magnet which together form the familiar eddy-current drag or brake. The damper disk, mounted on a spindle 24', is driven by pinion 25 and sector gear 26 at increased speed relative to expander shaft 3. (It is to be noted that any device which supplies suitable damping may be used in lieu of the above arrangement.) Motion of the expander shaft caused by displacement of clasp head l9 causes spring I! to exert a counter-restraint on control shaft l3 by means of expander crank 21 attached thereto. This counter-restraint compensates for the, restraint exerted by spring l5, and thus the piston 6 assumes a velocity determined by system constants and torque applied to the control shaft. I adjust the degree of compensation as follows: A crank 28, fixed to the shaft [8 islconnected by means of spring 29 and set plunger- 30 to a fixed element 3 I; thus by varying the setting of plunger 30 the tension of spring 28 may be varied and with it the degree of compensation. Since the operation of the expander is such that piston 6 tends to have a velocity proportional to the control shaft 13 input torque, the transducer has, from a long time or steady-state point of view, a displacement of the output element approximately proportional to the torque impulse or area under the torque-time curve of the torque input.

plunger 32 constitutes this secondary input element of the transducer. As shown in Figure 1, a differential link 33 is pivotally mounted at one end, on a pin 34, to an extension on the clasp head I9, and is connected at the other end to the drive plunger 32 by means of a drive pin 35 on the plunger lying within a slot 36 in the link 33. The.

control shaft i3 is provided with a limit crank 31 which has a limit crank pin 38 arranged to engage a longitudinal slot 39, in the differential link 33. If the slot is made narrow enough, measured across the differential link 33 to permit limit crank pin 38 no freedom except longitudinally of the differential link and radially with respect to pivot pin 34, then the control shaft is restrained to turn in relation to the tangential movement of the slot 39 which is determined by the relative motions of the drive plunger 32 and clasp head [9. Under these conditions let plunger 32 be displaced. This causes control shaft l3 to rotate, regardless of other control torques or restraints which are effectively overpowered, and to displace pilot 3 causing piston 6 to move in a direction such that the control shaft I3 is restored to its former position. Thus displacement of the secondary input element of the transducer produces an approximately proportional displacement of the output element. Now if the slot 39 is widened as shown in Figure 1 so as to permit tangential or lateral as well as radial freedom of limit crank drive pin 38, then torques applied to control shaft l3 may operate the transducer up until the point where the limit crank drive pin engages either of the upper or lower surfaces of the slot. Under the widened slot condition, displacement of the drive plunger must exceed a value dependent upon the displacements of the clasp head and limit crank before it can take over the control of the transducer. When the drive plunger is displaced sufiiciently, however, it automatically takes control and changes the characteristic of the transducer. To help centralize the drive plunger when not in use, centering springs 59 are used.

In an earlier paragraph the use of dither in the hydraulic power amplifier is discussed and it is stated that dither is sometimes introduced by vibrating the sleeve 2. Dither, for the purposes stated or for other purposes, may sometimes be introduced alternatively by vibrating longitudinally the zero set screw 2| by placing it in journals which are translated in vibratory motion by any well-known means. Figure 3 illustrates one possible means. Zero set screw 2| is carried in journal frame 6| which is free to move vertically in guides 60. An eccentric 33, turned by a shaft connected to a source of rotation not shown, imparts vibratory motion to journal frame 61 by means of connecting rod 62. This method of dithering is advantageous especially in cases where the sleeve 2 can be then made a part of the housing 8, eliminating the sliding fit shown in Figure 1.

g In order to provide terminology to describe the several ideas discussed above the chief terms are defined as follows:

Spring coupling is used to designate the mechanism of a characteristic transformer which uses spring linkage between the input and output elements of a power amplifier to achieve a derived characteristic of an output displacement approximately proportional to the input torque (or other quantity), the mechanism being equivalent to that shown in Figure 1 and described above.

Expander is used to designate the mechanism of a characteristic transformer which uses damped counter spring coupling between the input and output elements of a power amplifier to achievea derived characteristic of an output displacement dependent upon the torque impulse or area under the torque-time curve of the input torque for long time or steady-state conditions, the mechanism being equivalent to that shown in Figure 1 and described above.

Differential linkage is used to designate the mechanism of a characteristic transformer which uses a differential link to couple the input and output elements of a power amplifier to an input element of a transducer in order to achieve a derived characteristic of an output displacement approximately proportional to the input displacement, the mechanism being equivalent to that shown in Figure 1 and described above.

Auto transition is used to designate the process of change-over from one characteristic to another in a transducer by means of an apparatus equivalent to the differential linkage mechanism shown in Figure 1 and described above.

Spring transmitted dither is used to designate the method of introducing dither described above or any equivalent method wherein transmission through a spring or system of springs is used.

It is to be noted that if the expander shaft I8 is prevented from rotating by a clamp or if the parts associated with the expander are removed, specifically springs 22 and I1, and spring l6 made correspondingly stiffer, the derived characteristic of the transducer described as the short time or transient characteristic becomes the only characteristic. Under this condition the transducer has a derived characteristic of output displacement proportional to input torque for both short time or transient and long time or steady-state considerations. The auto transition and differential linkage mechanism may remain unchanged, however.

When the expander is allowed to operate or is retained as part of the transducer its effect may be interpreted in terms of the steady-state frequency response of the transducer. If the ratio of output displacement to input torque is considered as a function of frequency, it will be found that as the frequency is lowered 'a point is reached where the magnitude of the ratio rises. At zero frequency and with perfect adjustment, the magnitude of the ratio would rise to infinity. It is this increase in magnitude that suggests the term expander. Associated with the rise in magnitude of the ratio is a phase shift approaching ninety degrees at zero frequency in case of perfect adjustment. If the adjustment is not perfect, the magnitude reaches a peak value less than infinity and the phase shift drops as zero frequency is approached. However, considerable expansion" of the magnitude of the ratio may be obtained with not quite perfect adjustment and herein lies the value of the device.

To illustrate the use of the transducer of Figure 1 in an automatic control system a schematic diagram of a possible systemis shown in Figure 2. This figure shows a profiler and an automatic control system used to position the cutter in accordance with a template. The object of this system is to provide a rapid and accurate means of positioning the cutter when the work is passed b it.

A profiler head 40, carried on vertical ways 6i, carries a cutter 42 and suitable means for rotating it. The work 43 is fastened to the table M which is moved longitudinally in horizontal ways under the cutter. Also carried on the table M is a template or pattern t which is shaped to produce the desired form in the work. In contact with the template is a template follower 66 which is connected to a comparator 31, which like the cutter 42, is carried by the profiler head till. The comparator produces an electrical signal that is a function of the error or difference between the actual position of the profiler head and the position the profiler head should have according to the template. The electrical signal is transmitted to an electronic amplifier 38 where it is amplified in power and perhaps operated on by suitable networks. The output of the electronic amplifier actuates a control motor 69 which in turn puts a torque on the control shaft l3 of the transducer. Details of the transducer are shown in Figure l. The output i of the transducer con trols the displacement of a variable displacement pump 50 which is powered by an electric motor 5|. The motor also powers the auxiliary pump 52 which supplies oil for the transducer from the sump 53 and for the replenishment of the variable displacement pump. The output of the variable displacement pump drives a hydraulic motor 54 of the piston and cylinder type which controls the position of the profiler head 40. The pump 50, motor 5d and their operating parts, constitute what is commonly known as a servo-motor. The operation of the system is such that whenever an error is detected by the comparator 67 each component of the system tends to operate on its neighbor in such a way that the hydraulic motor 54 moves the profiler head 40 in such a direction as to reduce the error. By proper design of the components, of which the transducer is one, a rapid and accurate system may be obtained.

In order to prevent the profiler head from moving too far for any reason whatsoever, it is provided with limit stops in the form of cams 55 and 56, one of which, when the predetermined limit has been reached, engages cam follower 57, mounted on ways 4| or other fixed part of the machine, and thus through intervening linkage 58, moves drive plunger 32, constituting the secondary input of the transducer, in such direction as to cause the variable displacement pump 50 8 put element, a drive plunger, and connections between the control shaft, the drive plunger and the differential link.

2. A transducer comprising a power amplifier having input and output elements, a control shaft, a crank on the control shaft, a mechanical link connecting the control shaft crank and the amplifier input element, a spring connecting the amplifier output element and the control shaft arranged to apply torque about the control shaft approximately proportional to the displacement of the output element, a differential link pivotally mounted on the amplifier output element, a drive plunger, a drive pin on the drive plunger, a limit crank on the control shaft, a limit crank pin on the limit crank, and slots in the differential link for the drive pin and the limit crank pin respectively.

3. A transducer comprising a power amplifier having input and output elements, a control shaft, a crank on the control shaft, a mechanical link connecting the control shaft crank and the amplifier input element, a spring connecting the amplifier output element and the control shaft arranged to apply torque about the control shaft approximately proportional to the displacement of the output element, an expander shaft, an expander crank on the control shaft, a spring connecting the amplifier output element and the expander shaft, a spring connecting the expander shaft and the expander crank, a. differential link pivotally mounted on the amplifier output element, a drive plunger, a drive pin on the drive plunger, a limit crank on the control shaft, a limit crank pin on the limit crank, and slots in the differential link for the drive pin and the limit crank pin respectively.

4. An automatic control system for positioning a controlled element in accordance with a predetermined pattern, comprising a comparator that produces a signal that is a function of the difference between the actual position of the controlled element and its prescribed position as indicated by the pattern, means for generating a force that is a function of the comparator signal, a transducer comprising primary and secondary input elements and a power amplifier having input and output elements, means for applying the generated force to the primary input of the transducer, means connecting the power amplifier input element and the transducer primary input element, limit stops on the controlled element, means actuated by the limit stops for actuating the secondary input element of the transducer, differential linkage interconnecting the transducer secondary input element and the power amplifier input and output elements, and a servo-motor controlled by the power amplifier output element for positioning the controlled element.

5. An automatic control system for positioning a controlled element in accordance with a predetermined pattern, comprising a comparator that produces a signal that is a function of the difference between the actual position of the controlled element and its prescribed position as indicated by the pattern, a hydraulic motor for positioning the controlled element, a variable displacement pump for driving the hydraulic motor, a control motor having a control shaft, an electronic amplifier responsive to the comparator signal controlling the torque exerted by the control motor, a power amplifier having input and output elements, a connection between the control shaft and the amplifier input element, spring coupling between the amplifier output element and the control shaft, 9. connection between the amplifier output element and the variable displacement pump, limit stops on the controlled element, a drive plunger actuated by the limit stops, and diiierential linkage interconnecting the drive plunger, the control shaft and the amplifier output element. 7

6. A transducer comprising a power amplifier having input and output elements, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the input element for controlling the application of energy from the source of energy to the motor, and mechanism interconnecting the input element and the output element of the power amplifier having the property, under static conditions, of applying a force to the input element approximately proportional to the displacement of the output element, said force tending to move the input element in a direction such that the displacement of the output element would increase, said mechanism having the additional property, under non-static conditions, of applying a force to the input element dependent upon the present displacement and past displacements of the output element.

7. A transducer comprising a power amplifier having input and output elements, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the input element for controlling the application of energy from the source of energy to the motor,

mechanism interconnecting the input element and the output element of the power amplifier mately proportional to the displacement of the output element, said force tending to move the input element in a direction such that the displacement of the output element would increase, said mechanism having the additional property, under non-static conditions, of applying a force to the input element dependent upon the present displacement and past displacements of the output element, and other mechanism interconnecting the input element and the output element of the power amplifier having the property of applying a force to the input element approximately proportional to a displacement of the output element, said force tending to move the input element in a direction such that the displacement of the output element would decrease.

8. A transducer'comprising a power amplifier having input and output elements, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the input element for controlling the application of energy from the source of energy to the motor, mechanism interconnecting the input element and the output element of the power amplifier having the property, under static conditions, of applying a force to the input element approximately proportional to the displacement of the output element, said force tending to move the input element in a direction such that the displacement of the output element would increase, said mechanism having the additional property, under non-static conditions, of applying a force to the input element dependent upon the present displacement and past displacements of the output element, other mechanism interconnecting the input element and the output element of the power amplifier having the property of applying a force to the input element approximately proportional to a displacement of the output element, said force tending to move the input element in a direction such that the displacement of the output element would decrease, and means for adjusting the force on the input element developed by the first mechanism relative to the force onthe input element developed by the second mechanism.

9. A transducer comprising a power amplifier having input and output elements, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the input element for controlling the application of energy from the source of energy to the motor, mechanism interconnecting the input element and the output element of the power amplifier having the property, under static conditions, of applying a force to the input element approximately proportionalto the displacement of the output element, said force tending to move the input element in a direction such that the displacement of the output element would increase, said mechanism having the additional property, under non-static conditions, of applying a force to the input element dependent upon the displacement of the output element in such a manner that the quantity, a constant muliplied by the time-rate-of-change of the force plus the force, is approximately equal to a constant times the displacement of the output element, and other mechanism interconnecting the input element and the output element of the power amplifier having the property of applying a force to the input element approximately proportional to the displacement of the output element, said force tending to move the input element in a direction such that the displacement of the output element would decrease.

10. A transducer comprising a power amplifier having input and output elements, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the input element for controlling the application of energy from the source of energy to the motor,

a control shaft, a mechanical link connecting the control shaft and the input element of the power amplifier for transmitting movement from said control shaft to said input element, a spring connecting the output element of the power amplifier and the control shaft so arranged that a displacement of the output element produces a force on the control shaft tending to move it in a direction such that the power amplifier would be caused to act to decrease the displacement of the output element, an expander shaft with damping means connected thereto, a spring connecting the expander shaft and the output element of the power amplifier, and a spring connecting the expander shaft and the control shaft so arranged that the displacement of the output element in the steady-state produces a force on the control shaft tending to move it in a direction such that the power amplifier would'be caused to act to increase the displacement of the output element.

11. A transducer comprising a power amplifier having input and output elements, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the input element for controlling the application of energy from the source of energy to the motor, mechanism interconnecting the input element and the output element of the power amplifier .which has the property of applying a force to the input element approximately proportional to the displacement of the output element in a manner tending to move the input element so that the displacement of the output element would be altered. and which would leave the power amplifier, per se, in operable condition, if removed, a source of vibration, and additional mechanism interconnecting the input element of the power amplifier and the source of vibration having the property of producing a vibratory component of force on the input element, said additional mechanism comprising a spring-like device.

12. A transducer comprising a power amplifier having input and output elements, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the input element for controlling the application of energy from the source of energy to the motor, a control shaft, a mechanical link connecting the control shaft and the input element of the power amplifier for transmitting movement from said control shaft to said input element, a spring connecting the output element of the power amplifier and the control shaft for introducing forces on said control shaft dependent upon the displacement of said output element, vibratory means, and a spring connecting the vibratory means and the control shaft for introducing dither into the power amplifier.

13. A transducer comprising a primary input element, a secondary input element, an output element, a motor for moving the output element, a source or" energy for the motor, a regulating means operated by the primary input element for controlling the application of energy from the source of energy to the motor, mechanism interconnecting the primary input element and the output element for applying to the primary input element a force approximately proportional to the displacement of the output element in a manner tending to afifect the primary input element in its control of the output element, and means for interconnecting the secondary input element, the primary input element, and the output element so that the primary input element is able to be differentially positioned by the secondary input element and the output element.

14. A transducer comprising a primary input element, a secondary input element, an output element, a motor for moving the output element, a source of energy'for the motor, a regulating means operated by the primary input element for controlling the application of energy from the source of energy to the motor, mechanism interconnecting the primary input element and the output element for applying to the primary input element a force approximately proportional to the displacement of the output element in a manner tending to aiiect the primary input element in its control of the output element, and means operated by the secondary input element when the movement of a member of the mechanism connected to the output element exceeds preset limits for interconnecting the secondary input element, the primary input element, and the output element so that the primary input element is differentially positioned by the'secondary input element and the output element.

15. An automatic control system for positioning a controlled element in accordance with input data comprising a comparison means for roducing a signal that is a function of the difierence between the actual position of the controlled element and its prescribed position as indicated by the input data, a motive means forv driving the controlled element which includes a servo-motor connected to the controlled element, a source of energy for the servo-motor, and control mechanism for regulating the energy supplied from the source of energy for the servo-motor to the servo-motor, an amplifier means for actuating the control mechanism of the motive means having an amplifier motor connected to said control mechanism, a source of energy for the amplifier motor, regulating means for varying the energy supplied by the source of energy for the amplifier motor to the amplifier motor, mechanism interconnecting the output element of said amplifier motor and the input element of said regulating means for modifying the response of the amplifier motor to the regulating means, and force means connected to said input element of said regulating means for exerting a mechanical force on said input element that is a function of the signal produced by the comparison means.

16. An automatic control system for positioning a controlled element in accordance with input data comprising a comparison means for producing a signal that is a function of the difference between the actual position of the controlled element and its prescribed position as indicated by the input data, a motive means for driving the controlled element which includes a servo-motor connected to the controlled element, a source of energy for the servo-motor, and control mechanism for regulating the energy supplied from the source of energy for the servo-motor to the servo-motor, an amplifier means for actuating the control mechanism of the motive means having an amplifier motor connected to said control mechanism, a source of energy for the amplifier motor, regulating means for varying the energy supplied by the source of energy for the amplifier motor to the amplifier motor, mechanism interconnecting the output element of said amplifier motor and the input element of said regulating means for modifying the response of the amplifier motor to the regulating means, which includes a spring connecting said output element and said input element arranged to apply a force to the input element approximately proportional to the displacement of the output element, and force means connected to said input element of said regulating means for exerting a mechanical force on said input element that is a function of the signal produced by the comparison means.

17. An automatic control system for positioning a controlled element in accordance with input data comprising a comparison means for producing a signal that is a function of the difierence between the actual position of the controlled element and its prescribed position as indicated by the input data, a motive means for driving the controlled element which includes a servo-motor connected to the controlled element, a source of energy for the servo-motor, and control mechanism for regulating the energy supplied from the source of energy for the servo-motor to the servo-motor, an amplifier means for actuating the control mechanism of the motive means having an amplifier motor connected to said control mechanism, a source of energy for the amplifier motor, regulating means for varying the energy supplied by the source of energy for the amplifier motor to the amplifier motor, mechanism interconnecting the output element of said amplifier motor and the input element of said regulating means for modifying the response of the amplifier motor to the regulating means, which includes a spring connecting said output element and said input element arranged to apply a degenerative force to the input element approximately proportional to the displacement of the output element, said degenerative force tending to move the input element in a direction such that the regulating means would be operated to cause the displacement of the output element to decrease, and apparatus for applying a regenerative force to the input element approximately proportional, in the steady-state, to the displacement of the output element, said regenerative force tending to move the input element in a direction such that the regulating means would be operated to cause the displacement of the output element to increase, said apparatus including a damping means, a spring connecting said damping means and said input element, a spring connecting said damping means and said output element, and force means connected to said input element of said regulating means for exerting a mechanical force on said input element that is a function of the signal produced by the comparison means.

18. An automatic control system for positioning a controlled element in accordance with input data comprising a comparison means for producing a signal that is a function of the difference between the actual position of the controlled element and its prescribed position as indicated by the input data, a motive means for driving the controlled element which includes a servo-motor connected to the controlled element, a source of energy for the servo-motor, and control mechanism for regulating the energy supplied from the source of energy for the servo-motor to the servo-motor, an amplifier means for actuating the control mechanism of the motive means having an amplifier motor connected to said control mechanism, a source of energy for the amplifier motor, regulating means for varying the energy supplied by the source of energy for the amplifier motor to the amplifier motor, mechanism interconnecting the output element of said ampliiier motor and the input element of said regulating means for modifying the response of the amplifier motor to the regulating means, force means connected to said input element of said regulating means for exerting a mechanical force on said input element that is a function of the signal produced by the comparison means, and limit means for stopping the movement of the controlled element when predetermined limits are exceeded, including a differential interconnecting the input element of said regulating means and the output element of said amplifier motor, and a third element controlled by mechanism actuated by movement of the controlled element.

19. An automatic control system for positioning a controlled element in accordance with input data comprising a comparison means for producing a signal that is a function of the differencebetween the actual position of the controlled element and its prescribed position as indicated by the input data, a motive means for driving the controlled element which includes a servo-motor connected to the controlled element, a source of energy for the servo-motor,-and control mechanism for regulating the energy supplied from the source of energy for the servomotor to the servo-motor, an amplifier means for actuating the control mechanism of the motive means having an amplifier motor connected to said control mechanism, a source of energy for the amplifier motor, regulating means for varying the energy supplied by the source of energy 14 for the amplifier motor to the amplifier motor, mechanism interconnecting the output element of said amplifier motor and the input element of said regulating means having the property of applying a force to the input element of said regulating means approximately proportional to the displacement of the output element of said ampliiier motor, said force tending to move the input element of said regulating means in a direction such that the displacement of the output element of said amplifier motor would decrease, force means connected to said input element of said regulating means for exerting a mechanical force on said input element that is a function of the signal produced by the comparison means, and limit means for stopping the movement of the controlled element when predetermined limits are exceeded, including a differential interconnecting the input element of said regulating means and the output element of said amplifier motor, and a third element controlled by mechanism actuated by movement of the controlled element.

20. A transducer comprising a primary input element, a secondary input element, an output element, a motor for moving the output element, a source of energy for the motor, a regulating means operated by the primary input element for controlling the application of energy from the source of energy to the motor, mechanism interconnecting the primary input element and the output element having the property of applying a force to the primary input element approximately proportional to the displacement of the output element, said force tending to move the primary input element in a direction such that the displacement of the output element would decrease, and means operatedby the secondary in-' put element when the movement of a member of the mechanism connected to the output element exceeds preset limits for interconnecting the secondary input element, the primary input element, and the output element so that the primary input element is difierentially positioned by the secondary input element and the output element.

GEORGE C. NEWTON, Ja.

REFERENCES CITED The following references are of record in the file of this patent:

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